timeout not working in SqlSensor?

Does the timeout param work the way I think it should in Airflow 1.8? My query just pokes at the poke interval indefinitely. I want it to timeout after a few hours and fail instead.
The code is basically
“””
task_name = SqlSensor(
conn_id='redshift',
sql=(
"""
select * from this_table where date=‘2018-12-18'
"""
),
task_id=’task_name',
dag=dag,
start_date=datetime(2016, 9, 25),
poke_interval=20,
time_out=45,
“”"
So after running the query a couple of times I would expect a failure, but that’s not what’s happening, it just keeps querying and querying every 20 seconds.
Thanks,
Scott